High frequency line conductor



Aug. 4, 1936. J, F, cooK, .JRl

HIGH FREQUENCY LINE CONDUCTOR Filed Jan. 20, 1931 .1 Il II Patented Aug. 4, 1936 UNITED STATES PATENT OFFICE HIGH FREQUENCY LINE `CONDUCTOR poration of New York Application January zo, 1931, serial No.'5o9,911

10 Claims.

This invention relates to radio frequency transmission lines of substantial lengths for centralized or multiple radio equipment, particularly for centralized radio receiving systems as employed heretofore in hotels, apartment houses, hospitals, etc. In such centralized radio installations a single aperiodic antenna has been used on the roof of the building installed with a plurality of radio receiving sets, in place of a plurality of antenna previously employed, one for each radio receiving set. The radio frequency currents from such single antenna first are passed through one or more suitable radio-frequency amplifying units or main or central coupling units, each of which,

l5 like the antenna, is common to a plurality of the Wall outlets and receiving sets distributed more or less throughout the building; and from such amplifier or ampliers the amplified radio frequency currents are passed thru a transmission line, usually balanced to ground, to the various outlets for connection to the local distributed receiving sets in the various rooms ofthe building;

the transmission line, on the way to the receiving sets, leading to local coupling units. From each wall outlet and to each individual radio receiving set the usual connections are made electrically as usualv to an antenna, ground and the public service electrical lines to furnish power in lieu of batteries for the set. Heretofore, from a single ordinary antenna, as many as eighty or more ordinary radio receiving sets have been operated with even better results than by providing a separate antenna for each set. Y

Heretofore the radio frequency transmission line or cable itself (between the radio frequency coupling unit at the single, common antenna, and the radio frequency coupling unit at the outlet to one of the radio receiving sets) has included a cable including'two wires insulated 40 from each other (as for antenna and ground), and a plurality of radio frequency loading-coil units or lumped inductances have been inserted in said line at frequent intervals at least every twenty feet of the length of the line or cable.

Such lumped inductance devices or load coils have been installed inside the walls of the building, along the path of the radio frequency transmission line between the main amplifier at the antenna and the various local couplingunits,

at the room outlets, the walls having been cut o pen to receive them at said frequent intervals, for their bulk did not allow of their installation by the ordinary methods of installing a cable. These radio frequency load coils were inserted in the line or cable either after the latter had installation, the cost of the load-coils themselves, l0

and the wall-defacement, all were highly objectionable. That is, altho excellent results attended the operation of such systems after they had been installed, yet the cost of installation was so high, for the above reasons, that ln some cases'l the installation was prohibited by reason of the high cost.

An object of the invention is to eliminate the above objectionable featuresand high cost while .preserving the necessary operativeness for the 20 radio frequency cable line extending thru the building walls from the single, common antenna and main or central radio frequency amplifier or amplifiers, to the various local radio frequency coupling units at the outlets to the radio receiving 25 .sets distributed more or less throughout the various rooms of the building. An object incidental to the above object is a` construction of a radio frequency line which will cause the elimination of such objectionable features. Y so In accordance with the invention, the above objects are accomplished by dispensing entirely with the previously used radio frequency loadcoils', and by providing such special construction of the radio frequency conductor or cable itself 35 that, although the new cable may be of more expensive construction than the cable previously employed in connection with the load-coils, nevertheless it can be installed in the building walls with as great facility as any ordinary housewiring 40 cable, and without need of any cutting of it into sub-lengths to permit insertion between the cut portions, of any load-coils or equivalent devices of any nature whatsoever. Instead of employing many sections of ordinary wire cables as hereto- 45 fore, between the load-coils located approximately everyl twenty feet more or less as heretofore, the cable is manufactured specially ,3nd preserved in a continuous length from the main or central apparatus at the single or central aperiodic antenna, 50

and installed in the building walls like an ordinary cable, but extending to the distributed local coupling units at the outlets for the several rooms so that it is not necessary to cut either the cable or the walls save at the various room outlets to the 55 individual radio receiving sets. Thus this novel and comparatively simple radio frequency transmission line to the distributed wall outlets from the single antenna. may be much more readily and cheaply installed, and consisting as it does only of the specially manufactured cable, it is employed to replace the formerly used line consisting of many load-coil apparatuses and a plurality of intervening cut sections of ordinary cable connecting the plurality of load coils in the transmission line from antenna to radio receiving Of the drawing, which includes various operative forms of the special cable constituting the radio frequency transmission line between antenna and room-wall-outlets,

Fig. 1 is a transverse section, partly in elevation, of a cable provided among other features with internal solenoids and an external metallic sheath for balancing the house-line to the ground of the radio antenna system;

Fig. 2 is a side view of a portion of the length of the special cable of Fig. 1, with parts brokenv away to present a side View of the interior construction of the composite cable including the insulating cores of the long solenoids of relatively minute cross-section;

Fig. 3 is a transverse section, partly in elevation, of a modified form of the composite cable of Figs. 1-2, and wherein an interior radio grounding wire is provided;

Fig. 4 is a diagrammatic view c-f the prior wellknown centralized radio receiving equipment, as modified by the combination in operative relations thereto, of the special house-wall cable-line hereof of any desired particular construction in accordance with the invention; and

Fig. 5 is a transverse section partly in elevation, of another and simplified modification of the special composite cable, additional to those of Figs. 1-2 and Fig. 3.

In Figs. l-2, the three cylindrical elements 5|, 5|, 52 of the aperiodic radio frequency composite cable are of jute about one half centimeter diameter, these figures being of enlarged scale for clearness of illustration. These cylinders all are enclosed in metallic sheath 53 to be described. The enclosed elements 5|, 5|, 52 may be of other brous or fabric material which is electrically insulating, and laterally fiexible and radially yieldable as any rope or rope-core. On two of these fiexible, insulating cylinders 5 5 ,extending the entire length of many feet of the cable, are wound respectively, two like solenoids of fine wire 50, 50, with their turns slightly spaced apart and insulated from one anotherbythejute or other insulating material of the respective cores 5i, 5|. These fine Wires may be ordinary round wire, preferably No. 18 B & S enameled copper wire the enameled coating constituting protection additional to the insulating cores against short-circuiting of the spaced apart solenoid turns when the entire composite flexible cable is bent in manipulation and installation. Also, as, shown in both Figs. land 2, each of the small coils of fine wires 50 may be provided with insulating sheaths such as the fabric insulation illustrated by the circles around each of them. The two solenoids 50 both are wound inthe same direction, as shown, so that the lines of force are in opposition. The third cylinder 52 of Figs. 1 2, does not carry any solenoid, but is in position with its periphery lying against the insulating sheaths around the two small coils 50, and enclosed with them inside the over-al1 metallic cable-sheath 53. As diS- tinguished from the modification of Fig. 3, element 52 is solely for the purpose of furnishing a more nearly cylindrical shape to the entire composite cable (as distinguished from the comparatively fiat shape, jointly, of the other two elements 5|) all for the purpose of facilitating drawing the composite cable tln'u Wall-conduits in analogy to the case of ordinary cylindrical cables. As shown, this third flexible cylindrical member 52 is of larger diameter than fiexible cylinders 5|, being of substantially the same diameter as the insulating sheaths for the two coils 50 on the two cores 5l in order. to provide a symmetrical or balanced and nearly round cross-section of the complete composite cable. All these long cylindrical units 5|, 5i, 52 of this embodiment of Figs. 1--2 are consolidated into a unitary flexible cable, by means of a long flexible envelope or sheath 53, Fig. 1, and at right, Fig. 2, which in this embodiment is of metal similar to the common flexible metal sheath of ordinary electrical cables, and inthe present invention serving as means for establishing a radio ground connection in a manner to be described, in connection with the description of the connection for the smali long solenoids which constitute the portions of the radio frequency transmission between the antenna and the outlets to the radio receiving sets as in the diagram Fig. 4. The metallic sheath 53 of Figs. 1-2 constitutes the means by which an antenna ground connection can be provided for each individual outlet to the various radio receiving sets in the various rooms; and similarly the ends of the little solenoids 5U, shown as in use, tangent to their coils, -at the room-end of the cable, are connected inside the wall to the interior of the room-outlets so as to provide the antenna connection for the radio receiving set which is plugged into the outlet.

In Fig. 4 the composite cable such as in Figs. 1-2, or Fig. 3 or Fig. 5, is shown at 8, B, 40 and 4| in its operative relation to the rest of the system which is shown as an example in part, which is sufiicient for the purpose here, of one of the prior systems of centralized or multiple radio installations wherein a large number of radio receiving sets distributed throughout a large building of many rooms are supplied from a single antenna on the roof. The apparatus shown in Fig. 4 is standard centralized radio equipment save for the incorporation of the special composite cable hereof.

The upper half of Fig. 4 illustrates a radio frequency amplifier or central coupling unit 5, l,

received radio impulses of various frequencies from the single aperiodic antenna at the top, on the roof of the building, by way of connection 2; this central or roof amplifier being located in the vicinity of the antenna as in the pent-house and therefore not requiring any long transmission line to said amplifier from the antenna. 'I'he composite cable 8 is shown diagrammatically -as extending (at right, from the roof, at the middle of the central top coupling unit) down, usually to other aperiodic radio frequency amplifying coupling units such as 35, and thence the same cable extends as at 4| to room-outlets and radio receiving sets located substantial distances Yfrom the roof, i. e., over substantial distances From the diagrammatic cable-showing :8, the iii-- sulating cylinders 5|, 5| of Figs. 1--2 are omitted for clearness, the two multi-looped lines indicate the two little solenoidsV 50 of Figs. 1-2, and the line between the two multi-looped lines indicates the exterior metallic portion of the cable to which the ground connection for the antenna can be connected at each extension coupling, as at 25, or at each room wall-outlet to which the special cable might lead, as at lower left of Fig. 4. In the form of composite cable of Figs. 1--2 (as distinguished from Figs. v3 and .5) this .exterior flexible metallic portion of the cable shown in the diagram by the intermediate line is the flexible metallic cable-sheath 53 around which may be clamped any ordinary ground-connection as common in ordinary house-'wiring for electric lighting. A ground connection thus can be clamped around any portion of the special cable here, i. e., at any portion of the building traversed by it, another example being the ground shown at the upper end of cable 8, in addition to the above -grounds at 25 and extreme lower left. At the upper end of cable 8 also is illustrated how the two fine-wire small solenoids 50, 50 (indicated by the multi-looped lines) are connected respectively to coupling coil And below, at 26 is indicated hcw one of said little solenoids is connected to the extension coupling As shown, special cable 8 extends down to the second radio frequency amplifier, or so-called extension coupling unit 35 (including tube 21, 211 and transformer 28--29 and parts 3B, 39) located at a substantial distance from the antenna and upper or central radio frequency amplifying coupling unitshown at top above it, and more or less central to a plurality of room outlets in its neighborhood. The Various radio frequencies received on antenna I, having been twice amplified, as common in centralized radio installations, (first by the amplifier at top adjacent the others, and then by amplifier 35 below), next pass to the radio frequency room-wall outlets such as 3| at the lower right, to which may be plugged in the radio receiving set for that room. Thus the special composite aperiodic cable 8, Fig. 4, of Figs. 1-2 (Figs. 3 or 5), constitutes the radio frequency transmission line from the antenna l, for any and all of the frequencies received thereby and amplified at radio frequency by the central coupling unit up in the pent-house, downstairs to the radio frequency extension amplifier 35 which supplies the plurality of wall-outlets such as 3| and 42, and the radio receiving sets plugged therein, with twice-amplified radio-frequency impulses of any particular frequency to which any of the local radio receiving sets may be tuned. The wall outlet 3| at lower right, Fig. 4, includes the antenna connection 32, the ground-connection 33, and the illustrated electric-light current connections shown.

The particular wall-outlet 3l is assumed to be close to the second or extension amplifying coupling unit 35, as is usually the case with one or more of the wall-outlets supplied by an extension amplifier or coupling unit, and therefore the connecton between 3| and 35 from switch 30 to 3| is short -(say less than twenty feet) and therefore said connection may be and is shown as,

fthe ordinary insulated twisted wire cord 30. But where the distance between extension coupling unit 35 and awall outlet as at 42 is long, as there assumed, (as over twenty feet), thenthe special cable of Figs. 1-2 (or Figs..3 or 5) as at 4|, Fig. 4, is used instead of the ordinary cord as at 30.

And from the single central coupling unit (upper half Fig. 4) and from special cable 8, Fig. 4, a length of a duplicate cable like 8, as at 4|), may lead leftward to at least another extension amplifying coupling unit indicated very diagrammatically at the left center and leading to another wall outlet like 3| but not shown; so that the special cable may connect a plurality of extension units to the central coupling unit at the top of Fig. 4.

And to single or common aperiodic antenna I, there may be and usually are connected a plurality of central coupling units like the amplifier at the upper half of Fig. 4, as indicated by 3 and 23; and to each of such additional central coupling units there may be connected a plurality of extension coupling units with a plurality of wall-outlets for each of the latter, similar to extension unit 25 and wall-outlet 3|, by means of the special cable hereof, as above described for the special cables 8, 40 and 42.

In Fig. 4, 24 indicates the 110 volt power input for the central coupling unit shown at the top 25 of the building with the antenna. Similar power connections are provided for the various central coupling units, extension coupling units, and

wall-outlets, but these are omitted for the sake 30 of clearness. y

In Fig. 4, at upper right in dotted lines at 9 is indicated one of the many lumped inductances or load coils which are eliminated when special cable 8 is employed, said devices 9 being necessary when the prior cables were used.

The special cables of Figs. 1--2, 3 and 5 not only possess the superficial construction shown but are adapted for cooperation as above with the apparatus of Fig. 4 as radio frequency lines of uniformly or continuously loaded cable constituting a balanced radio frequency transmission line; but before describing their construction for such purpose, the general construction of the cableforms of Figs. 3 and 5 will be described.

The form of Fig. 3 is similar to that of Figs. 1 2, including the two little insulated copper wire helices 50 wound on the flexible insulating cores, the insulating sheaths respectively around the coils 50, and the third flexible insulating cylinder 52; but in Fig. 3, the radio antenna ground conductor, instead of being constituted by a metal cable-casing or exterior sheath as at 53, Fig. 1. is constituted by a little metal wire 54 inside in! sulating cylinder 52 in the form of fabric; and in this case the external casing or sheath 541 of the assemblage of cable-parts need not be of metal but may be of insulating fabric, altho said sheath may be metal if desired as in Figs. 1 2. And the little wire 54 may be pluralized and placed inside any two or more of the insulating cylinders of Fig. 3.

In the form of Fig. 5, a cable is provided for each of the little solenoids or helices 50 of the fine wire of Figs. 1 2, and of 'Fig. 3, and in such case two like cables are extended alongside one another in an arrangement wherein the two solenoids of the two cables are related to one another like the two solenoids 56 of Figs. 1-3 and in a manner to be described and are connected as in Fig. 4. Here in Fig. 5 the coil 50 is wound on a flexible insulating core as in Figs. 1--3; and as in Figs. 12, (and permissively in Fig. 3), a metallic cable-casing or sheath, as at 55, envelops the little long coil 50 of Fig. 5, 55 being insulated from Silas by the enamel coating of the No. 18

B S copper wireSU. If desired, and as shown, the sheath 55 when metallic may be insulated from coil 50 by the insulating tube shown in Fig. 5 around the coil. It is not necessary, however, that sheath 55 be metallic, for it may be fabric as in Fig. 3; and when it is desired to incorporate a conductor in this cable, as means for connection to ground connections, and when sheath 55 is nonmetallic, such conductor may be in the form of a wire 54, as shown, in the center of the insulating core on which coil 5l is wound, in analogy to the grounding wire 54 of Fig. 3 inside the insulating cylinder 52.

Any of the above cable-forms or their equivalents may be employed, as continuously and uniformly loaded and balanced described above and shown in Fig. 4, as radio frequency transmission lines between the amplifying coupling units respectively adjacent the multiple room-outlets and the single aperiodic antenna I (or the coupling unit adjacent the latter), or between the extension radio frequency amplifying units and their wall-outlets as when the distance between the same is in excess of twenty feet, or under any such conditions when the radio frequency transmission line is of such length as to require the old lumped load-coils in the alternative to the continuously and uniformly loaded cable hereof. Whether the two little long coils are both in the vsame cable as in Figs. 1-3 or each in a separate cable as that of Fig. 5, they extend alongside one another in the wall conduit indicated in Fig. 4 around cables 8 and 4I, the adjacent cable-coils or solenoids inside the wall-conduit being wound in the same direction so as to avoid inductive coupling between them.

As to adapting the cable construction shown for any such uses, and when for example as above the flexible insulating core on which the little helix of ilne copper wire is wound is about onehalf centimeter in diameter, and the wire No. 18 B S enameled copper wire, the coil may have approximately six turns per centimeter of length of its core or about 3500 turns for every twenty feet of length of core, that is, 175 turns per foot, or an inductance of about fty microhenries for every twenty feet, or two and one half microhenries per linear foot of core. This inductance is uniformly and continuously distributed along the entire length of the cable so that there is complete elimination of all lumped radio frequency inductance and the cable is uniformlyV and continuously loaded with radio frequency inductive reactance.

The wall-outlets of any such system as that of Fig. 4 may be tapped into the special cable hereof at any point of the cable, Without causing reflections.

The number of turns per foot in each coil 50 in any given case will depend upon the electrical constants of the wire and of the circuits to which the cable is connected, and upon the size of the wire, and the insulation around it, and the diameter of the insulating core on which the wire is wound.

A special cable of the long length as used in such systems as that of Fig. 4, and having a coil of a diameter of only about one half centimeter for example, as above, is in effect a solenoid'iniinitely long relative to its diameter. The inductance of such a solenoid is given by the formula:

where a is the radius of core 5l in inches, n is the number of turns of the entire inductor, and

l the length of the wire. From this it will be seen, with reference to the above gure of 175 turns per foot of a helix of about a half centimeter diameter, that a larger helix on flexible in- 5 sulating core 5| with a smaller number of turns per foot of core could be used, if permitted by suilicient diameter of the cable or the internal diameter of the wall-conduit through which the cable is to be drawn; and conversely, if a smaller diameter of conduit and core be used, the number of helical turns per foot must be increased in this continuously and uniformly loaded radio frequency transmission line.

Furthermore, the distributed radio frequency inductance per unit length of the cable hereof as a means for transmitting over substantial distances, the impulses received by the aperiodic antenna I to the plurality of radio receiving sets, will be influenced by the broadcast frequency 20 band which the central and extension coupling units are designed to handle. For example, if said coupling units be of low impedance then the composite cable hereof should have a low value of inductance per unit length.

The various radio receiving sets plugged in to the outlets of a centralized radio receiving installation, (Fig. 4), as at lower left, in use are tuned to various of the frequencies received by the single aperiodic antenna and handled within a given frequency band by the central and extension coupling units, and the cable hereof is capable of transmitting simultaneously to said receiving sets all said various frequencies, which also are simultaneously received by said antenna. And such cables can transmit simultaneously a plurality of different frequencies between any plurality of radio apparatuses and an antenna. This cable also is adapted to transmit radio impulses effectively between any radio frequency apparatuses and a remote antenna.

I claim:

l. A flexible aperiodic high frequency cable for radio transmission lines of centralized radio installations and including at least two adjacent flexible cores of insulating material and including also at least two aperiodic radio frequency conductors respectively wound helically around the lengths of said adjacent cores in the same direction preventing coupling effects between the helices, flexible means insulating said solenoids from one another, the successive turns of each solenoid being insulated and only slightly spaced from one another, said solenoids constituting continuously and uniformly loaded radio frequency cable; and a flexible tubular casing of metal sheathing said adjacent cores and solenoids and insulated from the latter,` said metallic casing constituting a balancing element of the radio frequency cable.

2. A exible aperiodic radio frequency cable including at least one exible core of insulating material and including also at least one flexible aperiodic radio frequency transmitting conductor, said conductor being wound helically around the 65 length of said core with turns only slightly spaced from one another and into a solenoid of substantially infinite length relative to its diameter, the successive turns of the solenoid being insulated from one another, and the solenoid itself ex- 70 tending continuously along the length of the cable constituting a continuously and uniformly loaded radio frequency cable; a flexible tubular casing of metal as an element of the cable and sheathing said solenoid and its core and consti- 76 Y ing as an element of the cable parallel 'with said solenoid, the combination constituting a flexible balanced radio frequency aperiodic cable properly loaded with radio frequency inductive reactance distributed along the length of the cable by means of the radio frequency inductive reactance of said solenoid itself.

4. A flexible aperiodic radio frequency cable adapted for the ordinary methods of installing house-wiring, which includes a hollow flexible metallic retainer as ordinary metallic flexible cable-sheath, and at least one aperiodic solenoid of small diameter enclosed thereby and having a large number of turns of good conductor wire per inch of length of the flexible cable and slightly spaced apart, such solenoid being flexible, and extending continuously along the length of the cable; said flexible metallic cable-sheath constituting a balancing conductor in the combination, and the combination constituting a balanced aperiodic, flexible radio frequency cable properly loaded with radio frequency inductive reactance distributed along the length of the cable by means of the radio frequency inductive reactance of said long small solenoid itself.

5. A flexible radio frequency aperiodic cable adapted fox` the ordinary methods of installing house-wiring, which includes two solenoids of small diameter and of small good conductor wire located alongside one another and wound in the same direction causingvopposition of radio frequency lines of force preventing radio frequency inductive coupling between the adjacent solenoids, each of said solenoids having a large number of turns of small diameter per inch of length of the cable and slightly spaced apart and such solenoids being flexible and extending continuously along the length of the cable constituting a radio frequency aperiodic cable properly loaded with radio frequency inductive reactance distributed along the length of the cable by means .of the radio frequency inductive reactance of said long small solenoids themselves. v

6. A flexible radio frequency aperiodic cable adapted fo-r the ordinary methods of installing house-wiring, which includes two solenoids of small diameter and small good conductor wires extending continuously along the length of the cable, and a flexible metallic retainer as ordinary flexible metallic cable-sheath enclosing both solenoids in positions alongside one another, the two solenoids being wound in the same direction causing opposition of radio frequency lines of force and preventing radio-frequency coupling effects between the adjacent solenoids, and the metallic cable-sheath constituting a balancing conductor for the radio frequency cable; the exible solenoids having a large number of turns of small diameter per inch of length of the cable and retainer and slightly spaced apart and such solenoids being flexible; the combination constituting a balanced radio frequency flexible aperiodic cafw 5 b, Piil loads@ with i fllmy. ance distributed ,along the length of'thehcable by means of the radio frequency reactance of said long small 'solenoids themselves.

"7. A exible radio frequency aperiodic cable adapted forth'ecrdlnarymethods of installing house-wiring, which includes two o vsolenoids or small diameter and small Agoed conductor and extending continuously along the length of the cable; three exible cylinders of small diam# eter arranged inA angroup wherein each cylinder lies adjacent both of the other two, 'at least two of 'said flexible cylinders beingof insulating material; and a flexible retainer as ordinary flexible cable-sheath enclosingl said group of cylinders and 'said solenoids; the slaan wires or said sclenoids being wound in the same direction respectively on said two adjacent insulating cylinders as cores, causing opposition of radio frequency lines of force and preventing radio frequency such solenoids being flexible; said third cylinder filling out the retainer to the general cross-section of a cable, and said long small solenoids constituting un-coupled flexible radio frequency aperiodic conductors properly loaded with radio frequency inductive reactance distributed along the length of the cable by means of the radio frequency reactance of said long small solenoids themselves.

8. A flexible aperiodic radio frequency cable adapted for the ordinary methods of installing house wiring, which includes two solenoids of small diameter and small good conductor wires and extending continuously along the length of the cable; three flexible cylinders of small diameter arranged in a group wherein each lies adjacent the other two, at least two of said cylinders being of insulating material; a straight flexible metallic wire enclosed by one of said flexible insulating cylinders as balancing conductor for the radio frequency cable; and a exible retainer as an ordinary exible cable-sheath enclosing said group of cylinders and said solenoids; the small wires of said solenoids being wound in the same direction respectively on two of said adjacent cylinders as cores, causing opposition of 5 radio frequency lines of force and preventing radio frequency coupling effect between the adjacent solenoids, and each solenoid having a large number of turns of small diameter per inch of length of its core and of the cable and slightly 5 spaced apart, such solenoids being flexible, said cable being properly loaded with radio frequency inductive reactance distributed along the length of the cable by means of the radio frequency inductive reactance of the long small solenoids themselves.

9. A exible radio frequency aperiodic cable adapted for the ordinary methods of installing house-wiring, which includes two solenoids of small' diameter and small good conductor wires 65 and extending continuously along the length of the cable; three flexible cylinders of which at least two are of insulating material, said three cylinders being arranged alongside one another in a group; and a flexible metallic retainer as ders as cores, causing opposition of radio frequency lines of force and preventing radio fregquency coupling effect between the adjacent solenoids, and each solenoid having a large number of turns of small diameter per inch of length of the cores and of the cable and slightlyY spaced from one another, such solenoids being flexible; said cable being properly loaded with radio frequency inductive reactance distributed along the length of the cable by means of the radio frequency inductive Ereactanee of the long small solenoids themselves. f Y

10. A flexible radio frequency aperiodic'line adapted for the ordinary methodsiof installing house-wiring, which includes two cables each including a flexible retainer as ordinary iiexble cablesheath; and a. iiexible solenoid of small di- JosEPH FL cooKL Jn. 15 

